a. Field of the Invention
The present invention pertains generally to windows with vertically operating sashes and more particularly to counterbalance devices for the sash of vertically sliding windows.
b. Description of the Background
Counterbalance mechanisms have been used for the sash of vertically sliding windows for a substantial period of time. Many of the previous techniques of counterbalancing have used counterbalance weights that are connected by ropes, cords, ribbons, bands, chains, etc. (“connectors”) to the sash of the window. The purpose of the counterbalance is to provide a sufficient upward force that counterbalances the weight of the sash so that the sash can be easily lifted and maintained in a stationary position.
Many problems exist with these types of counterbalanced mechanisms. For example, oftentimes the connector breaks rendering the counterbalance mechanism ineffective. If the connector breaks when the window is in a closed position and the weight is sufficiently heavy, the weight can fall down through the weight pocket, through the bottom of the window frame and into the wall. Fixing such systems may be difficult. For example, counterbalances that have the desired weight and that are capable of fitting through the opening of the weight pocket may not be readily available. In other words, prior art devices have not provided an easy way of adjusting the counterbalance force to an optimum level for sashes in a weight and pulley counterbalance vertically operating window system. In addition, it may be difficult to assemble these heavy counterbalance weights when attempting repair. Also, replacement of broken ropes or chains may be difficult. Further, if a window is broken, lighter or heavier glass may be used to replace the broken glass which, in turn, will cause the original counterbalance weight to improperly counterbalance the new weight of the sash. Hence, accurately selecting the correct counterbalance force and providing an adjustable manner of counterbalancing the weight of the sash with historic weight and pulley counterbalance vertically operating window systems, has previously been difficult. In addition, with heavy sashes, counterbalance weights typically require a diameter that is too large to fit into the opening of the window frame to provide sufficient counterbalance weight. If the necessary counterbalance weight is achieved with a smaller diameter, it will necessarily be longer to be of an adequate and effective weight to counterbalance a heavy sash. These longer weights significantly reduce the amount of travel of the sash because the longer weight will contact the bottom of the window frame, resulting in restricted opening of the window sash.